They say you're nothing but a party girl,
Just like a million more all over this world
Alison, I know this world is killing you,
Oh, Alison, my aim is true.
That got me that thinking that it's quite possible that many artists get objectively better after public boredom with them sets in. To take one small example to help explain the phenomenon that the fate of all artists, whether Elvis Presley or Tom Stoppard or Tim Burton/Johnny Depp, is to have people tell you they liked your early stuff best, I noticed in the 1990s that Elvis Costello had made himself a better singer now than in his 1977-1983 heyday. He likely has taken a lot of singing lessons since then and worked hard at his craft.
For all I know, he might be a better songwriter now than he was when he wrote the songs that eventually made him (mildly) famous.
The man and the moment had come together. Granted, in the big city of Houston in January 1978 there were only 200 or 300 people who would pay $3 to see Elvis Costello. But we were the right 200 or 300 people, the ones who wouldn't shut up about him.
So, that explains a fair amount about why artists, if they are lucky, mostly just get one short window of relevance.
For example, "Watching the Detectives" strikes me as a pretty terrible single, the most annoying Costello song of his early years, but it still gets played on some radio stations a lot for reasons, presumably, of path dependency: perhaps it was the first Elvis Costello song that many people became familiar with. By the standards of Oliver's Army or I Don't Want to Go to Chelsea or Beyond Belief or Strict Time, Watching the Detectives is a bad Costello song, but it's still a recognizably Costelloish song.
And it could be that that's what matters most: the artist has to reach some level of quality and then what carries him is largely the freshness of his personal style, which is heavily dependent on his unique personality. And after awhile, his personality doesn't seem so unique anymore, even if the quality increases.